As shown in FIG. 1 and 2, the conventional corrugated cardboard packing box has a knob 4 in which a portion of a solid line 5 is cut and a portion of a dotted line 3 is bent.
In order to use the knob 4, one pushes the cut solid line of the knob 4 from the exterior of the box to its the interior. Then, the portion of the knob 4 is bent at the dotted line so that a knob hole 2 is formed.
However, when a user uses the knob hole 2 to move an article in it, a stress is concentrated in both edges A, A' of the knob portion so that damage of the box is often generated.
As a result, the dotted line which have to be bent naturally is not bent and a connected line 6 of the rupture portions of both edges is bent. So, the conventional packing box has a problem that the appearance of the box is damaged and not elegant.